Block copolymers composed poly(alpha-monalkenyl at least two poly(alpha-monoalkenyl arene) blocks and at least one elastomeric poly(conjugated diene) block or hydrogenated or partially hydrogenated derivatives thereof have offered potentially attractive properties in sealant compositions but have found limited use in commercial application because conventional methods of applying the sealant directly to the substrate have failed to produce adequate long term adhesion especially on exposure to water. Formulations containing these block copolymers have excellent hardness, tensile, and flexibility properties but exhibit inadequate (less than 5 pounds per linear inch width (pli)) 180.degree. peel strength for most high performance sealant applications in tests against glass or aluminum after 7 days in water.
The composition of this invention retains the useful hardness, tensile and flexibility properties exhibited by the conventional block copolymer sealants and in addition shows satisfactory (greater than 20 pli) 180.degree. peel strength after 7 days in water.